Research On Hidden Cavity Detection And Theories Of Stability Prediction In Metal Mine

For mining industry, there are enormous contributions in increase of national economy, but in the condition of continuously exploiting underground resources to supply raw material for other industries, there are many mining cavities which are severely harmful to human production and life, so the researches, such as the technologies of cavity detection, characters of terrane motion, stability of pillars, time limit of cavity stability, and et al, which are concerned about treating cavities and the safety of demos'lives, are no time to delay. Therefore the detection technologies and stability prediction of hidden cavity in metal mine as the theme of this paper, the main contents are included as follows.Based on analyzing the present detection technology and characters of hidden mining cavity, a detection method of hidden cavity in metal mine, which high-dense resistance technique combined earthshock reflection method with drillhole validation, was put forward. Introducing fractal theory, the complex or anomalistic grades of mining cavity were analyzed with fractal box-dimension. Using the learning and memory functions of neural network model, an intellective forecast model of cavity boundary, which forecasted unknowable or unmeasured cavity outline, was established, so the limits of measure apparatus or work field were patched up, and the enormous advantages in decting and analyzing cavity was offered, at the same time, decting cost was saved, as well as the work efficiency was enhanced.Analyzing the intrinsic and extrinsic factors of stability in metal mine cavity, the motion in terrane were simulated with a finite element method of material description, and the change laws of stress and strain in different cavity area and roof high were revealed.Exploring breakage energy of rock, a criterion of breakage energy was estabilished, and the laws of energy release in cavity terrane were researched with a method of numerical simulation. The results showed that energy release in cavity terrane increased with augment of excavated bulk, and the rates of energy release raises in a way of quadratic curve. After mining cavity was filled, stress concentrations in terrane decreased in a certain extent, and there were tremendous effects that reduced the rates of energy release in cavity terrane.Selecting seven main influence factors to terrane moving, which are f coefficient of wall rock in upside and downside ore body, stability extent of terrane, exploiting deepness, excavating thickness, obliquity of ore body, length tend towards ore body and mining method, as input data, and using moving angles of upside and downside ore body as output data, a prediction model of moving angle in cavity terrane was established by a method of neural network. The results of validating with engineering examples show that the selected factors are reasonable, and the neural network method owns high precision. Using the model, the moving angle of terrane in Sanshandao Golden Mine and influencing range of subsiding cavity in Dabaoshan Mine were predicted and the theories of safe mining were provided.Cavities come into being repetitively excavated in rock mass, so the deformations of terrane behave complicated non-linear mechanical characters, and the processes of deformation in rock mass were unfolded with a theory of chaos. According to surveyed deformation data of cavity terrane in Daobaoshan Mine, a grey prediction model of time limit of cavity stability was established, and the stable time was predicted.According to underground mining method, pillars were classified, and the safety theories of upright pillar, artificial pillar and roof pillar were explored. Mechanical models of a single rock pillar and roof pillar were established, and strength design theory of single row pillars was studied. With the parameter R, which is the proportion rock pillars space to their size, the framework and reasonable collocation of pillars were analyzed, and the optimal value of R was 2.0 to 3.0, at the same time the mechanism of prefabricated pillars and their strength-design theories were researched.